Purification of



x This; i e tionre ates it th i re aai nr Patented Aug. .2 0, 1935 e Iv.

mum

' PURIFICATION OF r-N-METHYL i- HALoeE -AN HaArrnrDoNE;

Henry r w i anu, South Milwaukee; and Edwin 'QBuxbaum, shoreweoi'wis; asg t E- f du'Pont de Ne 'w s CgmpanfiWil 1 Del.,'a' corporation ofDelaware fn on l" I ixfoma iagaii iicatio oc olmr22,1934, seri mamama 1N methyl 4 halogen-anthrapyridones ar d more; Particu ar y; to. the pufi a f these compounds. $0; 139 the, same from those impurities which oncondensation with arylamines produce blue color bases. V

InJthe preparation of l-N-methyll bromo-f anthrapyridone by theacetylation of l-methylamino-4-bromo-anthraquinone and subsequent"ring-closure in alkaline solution, there is usually 7 present in theresulting product certaini compounds which on condensation withar'ylarnines and subsequent sulfonation produce blue dyestufis. inatesand which is objectionable in forming blue color bodies on condensationwith arylamines is the 1 methylamino 4 bromo-anthraquinone, .whichremains in the product either due to incomplete acetylation in theoriginal step or due to hydrolysis of the acetylamino-anthraquinonecompound on treatment with alkali in the ringclosure of the acetyl bodyto the anthrapyridone.

1-N-methyl-4-br0mo-anthrapyridone, when condensed with an'arylamine,such as para-toluidine, and sulfonated, produces a red dyestufigenerally known in the trade as Alizarine RubinolR (Color Index No.1091). Small amounts only of the blue component, therefore, whichresultsfrom the condensation of 1-methylamino-4-bromoanthraquinone withp-toluidine, materially alter the'shade of the desireddyestuff. Thissame difiiculty is experienced in preparing the correspending1-N-methyl-l-.chloro-anthrapyridone.

. For convenience, however, the invention will be exemplified inconnection with the I-N-methylis dissolved in sulfuric acid. and treatedwith an oxidizing. agent at temperatures'not materially abovel30 C., apurification is effected and the .l-methylarnino-4-bromo-anthraquin0neis converted to the l-methylamino-l-hydroxy compound, which under theconditions used in the condensation of the resulting products witharylamines will not form arylamino-anthraquinone bodies. The l-N-methyl4 bromo-anthrapyri- The impurity which apparently. predomwater,filtered, and washed acid free.

7 is stirred at 30 C. for one hour.

o e-is a a ta eou ly sepa a d f o t 5. ur a id so utio by b i i th idcocenr; tration t approximatel -ifizz,.asmoreiul do: i scribed incopending pp a ionfierilNoi 149 47 and as illustrated in the followingexamples.- 5

The following examples are given to more'fully illustrate our invention.The parts used are by weight. v V Example 1 50rparts of crudel-N-methyl-4-bromo-anthra- 10 pyridone are dissolved in 300 parts of 93%sulfuric acid at room'temperature. The temperature is raised to 90 overavperiod of; one-half v hour, and '10 parts of manganese dioxide areslowly added thereto over a period of one hour at 15 this temperature.The mass is then agitated at 90 for two hours and cooled to C. The acidreaction mass is poured into 3000 parts of cold V l 7 Example? 7 50parts of crude 1-N-methyl--bromo-anthrapyridone are dissolved in 500parts of 93% sulfuric acid. The temperature is raised to C. and 5 partsof manganese dioxide are. added slowly thereto over a period of onehour. The

temperature is then raised to 100 C. and held fortwo hours. The mass iscooled to C. and parts of wateradded over a period of one hourmaintaining the temperature at 80 C. It is then cooled to roomtemperature and agitated for eight, hours. The product is filtered-onwool or a Jena glass filter and sucked ry, and washed. withl00 parts of78% sulfuric acid. 1 35 The l-Nrmethyl l-bromo-anthrapyridone is thensludged in 3000parts of hot water, filtered,

washed acid free and dried. The purified1-N-methyl-l-brorno-anthrapyridone when .obtained in'this manner is abright pea green color Condensation of this product jwith primaryamines, such as'p-toluidine, shows complete rei'noval of the principalimpurity, namely, 1-'

methylamino-4-bromo-anthraquinone.

7 "Example;

parts of crude l-N-methyll-bromo-anthrapyridone are dissolved in 1000parts of 90% sulfuric acid at room temperatures. 10 parts of sodiumdichromate are slowly added-and the mass 50 V p I The temperature israised to -120 C. and' held for two hours. Theimass is cooled to 85C.and parts of water are slowly added while maintaining the temperature at85-90 C. It is then cooled to .55

and held at 30 for eight hours. The product is filtered, washed with 150parts of 78% sulfuric acid, sucked dry and sludged in 2000 parts of coldwater, filtered and dried. The purified l-N- methyl-4bromo-anthrapyridone is a pea green color. The condensation of thisproduct shows complete removal of such impurities of,l-methylamino-4-bromo-anthraquinone from the pyridone.

Other oxidizing agents such as alkali-metal permanganates, chromic acid,etc., may be substituted for the manganese dioxide and alkalimetaldichromates used in the above'examples.

These, however, require somewhat lower temperatures than given in thespecific examples. The temperatures used may vary from about 30 to 130C., the time in which the reaction may be completed also varying withthe change in temperature. Sulfuric acid of a concentration of to may beused in this reaction.

In the above examples the l-N-methyl-4- chloro-anthrapyridone may besubstituted for the corresponding bromo-anthrapyridone;

What we claim is:

1. In the preparation of 1-N-methy1-4-halogen-anthrapyridone, the stepwhich comprises subjecting a crude l -N-methyll-halogen-anthrapyridoneto the action of a relatively strong inorganic oxidizing agent insulfuric acid.

2. In the preparation of l-N-methyll-halogen-anthrapyridone, the stepwhich comprises subjecting a crude l-N-methyl--halogen-anthrapyridone tothe action of a relatively strong inorganic oxidizing agent in sulfuricacid at temperatures between 30 and C.

3. In the preparation of l-N-methyl-l-bromoanthrapyridone, the stepwhich comprises subjecting a crude 1-N-methyl-4-bromo-anthrapyridone tothe. action of a relatively strong inorganic oxidizing agent in sulfuricacid.

4. In the preparation of l-N-methyll-bromoanthrapyridone, the step whichcomprises subjecting a crude 1-N-methyl-4-bromo-anthrapyridone to theaction of a relatively strong inorganic oxidizing agent in sulfuric acidat temperatures between 30 and 130 C. v HENRY J. WEILAND.

EDWIN C. BUXBAUM.

